The renal pelvis is a visco-elastic organ and serves the double purpose of acting as a pump function and a reservoir. With a "pig-tail" catheter ("William Cook Europe" aps, Søborg, Denmark), placed transrenally in the canine pelvis and external blocking of the pelveoureteral junction, it is possible to change the volume of the canine renal pelvis and register the resulting pelvic pressure. This examination is called pelveometry. In 24 adult, female dogs pelveometry showed a linear relation within the range of 0-5.5 ml and 1-30 mmHg, respectively. The correlations between the measurements and the estimated lines were about or more than 90%. The registrations during increasing and the following decreasing volume change showed different values and another linearity of 50% of the assays. This observation demonstrated the occurrence of hysteresis (c: a viscoelastic reaction of the smooth muscle tissue) and is in accordance with findings in previous investigations of other smooth muscle organs. The linearity within physiological ranges of the two pelvic parameters indicates that the pelvic pressure and the frequency of ureteral peristalsis will be sufficient to describe the urodynamic patterns of the canine upper urinary tract.